1. The field of art to which the invention pertains includes the art of fluid handling as specifically directed toward tapping a pipe main under pressure.
2. Tapping T's for effecting a house outlet connection are available from a variety of manufacturers and are widely used for tapping gas service from underground gas mains. Exemplifying tapping T's of the prior art as principally adapted for metal pipe are those disclosed in U.S. Pat. Nos. 3,094,137; 3,264,907; 3,277,683; 3,295,398; and Re 26,224. Typically, such tapping T service connectors include a body having a side outlet house connection integral therewith and adapted for secured mounting onto the exterior of the pipe. The tapping tool is threadedly supported in the body for radial advancement against the pipe wall until effecting a penetration or cutting of a removable slug by which an opening is formed communicating with the branch connection. A characteristic requirement of such tapping T's is that the tool should be capable of penetrating and/or cutting the pipe wall at turning torque levels on the order of about 13 to 20 ft/lbs. This is within reasonable strength capability of an average workman using an 8 inches long wrench. At the same time, it is desirable to maintain these torque levels so that the operator will sense loss of torque signalling penetration of the pipe wall. Failure to sense penetration can, of course, result in overtravel with consequent damage to the piping system.
With the advent of plastic pipe and/or tubing and their approval by regulating governmental agencies for natural gas transmission, it has been found that tapping T tools of the prior art intended for retaining a cut slug from metal pipe are generally considered much too expensive for use with plastic pipe. That is, such tools for metal pipe are generally manufactured from high price steel which is carefully machined and heat treated. In keeping with the change to plastic pipe various tool designs of less expensive construction have been proposed. Among those adopted has been a more or less tubular end with a circular cutting edge but which has not proven entirely satisfactory on plastic pipe by virtue of the relatively high-torque levels it encounters in cutting a slug. At the same time, these tools have encountered extreme "breakaway" torques required to free the tool in the event tool turning is momentarily interrupted. Despite recognition of these problems, a ready solution in the form of a low cost slug retaining tapping T suitable for use with plastic pipe and operable within prescribed torque limits has not heretofore been known.